Cookie duration (also cookie life or attribution window) is the period after a click during which a conversion can still be credited to the referring affiliate. If a program has a 30-day cookie duration, a customer who clicks an affiliate link and buys within 30 days counts as that affiliate's sale; a purchase on day 35 does not.
How it works
When a visitor clicks a tracking link, the tracker records the click and typically sets a cookie that expires at the end of the program's window. At conversion, the system checks for a valid click inside the window and, under last-click attribution, credits the most recent qualifying affiliate.
The window is a rule enforced by the tracking system, not just a cookie setting. In S2S tracking, the click timestamp is stored with the click ID, so conversions arriving after the window can be rejected even when no browser cookie is involved.
Browser privacy features matter too. Safari's Intelligent Tracking Prevention caps cookies created through JavaScript at seven days, so a 30-day window that relies only on a script-set cookie can fall short in practice.
Example
Example: a program with a 30-day window.
| Click | Purchase | Days elapsed | Credited? |
|---|---|---|---|
| Mar 1 | Mar 20 | 19 | Yes |
| Mar 1 | Apr 5 | 35 | No |
Why it matters
For affiliates, longer windows help with considered purchases such as software, finance, or travel, where customers research before buying, so compare windows when choosing programs. For brands, the window is a cost lever: longer windows pay for more conversions that might have happened anyway, while very short ones make the program less attractive to content partners. In MassPartner, brands set cookie duration per campaign, with 30 days as the default.
Related: last-click attribution, tracking link, S2S tracking.